A test head assembly for a DUT board has a number of pin boards, each of which is equipped with a contact probe for contacting a DUT (device under test) board. A DUT is mounted thereon through the contact probes. In order to implement complete contact between the test head and the DUT board, the contact probes are supported by springs in such a manner as to be projected from and retracted into the pin board. The DUT board is fixedly mounted on the test head while pressed by the contact probes which are urged by the springs.
FIG. 1 shows a conventional mounting mechanism for mounting the DUT board on the test head. A docking plate 20 having a square-frame shape is provided on the upper surface of a DUT board mounting portion 1a of the test head 1, and a pair of cams 21 are mounted on the opposite sides of the docking plate 20. The DUT board 10 is fixed to a square supporter 22 at several points thereof in such a manner as to be removably mounted on the square supporter 22. The square supporter 22 is provided with cam followers 23 engagable with the cams 21, and the cam followers 23 are downwardly insertable into the cams 21. Upon rotation of the cams 21 by operating a lever 21a, the cam followers 23 are brought into engagement with cam grooves of the cams 21, and the supporter 22 is downwardly fastened along slopes of the grooves. The cams 21 are linked with each other through a wire 24, and thus operated interlockingly with each other.
However, the above conventional mounting mechanism has the following disadvantages. First, the supporter 22 having the cam followers 23 is indispensable for the mounting mechanism. In addition, a DUT board must be mounted and removed from the supporter 22 one by one for each DUT board 10 so that the operation is not efficiently carried out. Secondly, the cam 21, the lever 21a and the wire 24 project from the upper surface of the test head 1, and the projection of these elements restricts the access area. Likewise, the cam followers 23 project from the side surfaces of the supporter 22 and thus also restrict an access area. Thirdly the supporter 22 is urged by a force directed in a horizontal direction through the rotation of the cams 21, and this urging force causes a dislocation of the DUT board 10.
This invention is made to overcome the above disadvantages of the prior art, and an object of this invention is to provide a mechanism for removably mounting a DUT board in which a mounting and removing work or an exchange work of the DUT board is easily carried out, and the DUT board is stably mounted.